[RISCV] Move some vector test into the rvv test directory. NFC

diff --git a/llvm/test/CodeGen/RISCV/fixed-vectors-vadd-vp-mask.ll b/llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vadd-vp-mask.ll
similarity index 100%
rename from llvm/test/CodeGen/RISCV/fixed-vectors-vadd-vp-mask.ll
rename to llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vadd-vp-mask.ll

diff --git a/llvm/test/CodeGen/RISCV/fixed-vectors-vmul-vp-mask.ll b/llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vmul-vp-mask.ll
similarity index 100%
rename from llvm/test/CodeGen/RISCV/fixed-vectors-vmul-vp-mask.ll
rename to llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vmul-vp-mask.ll

diff --git a/llvm/test/CodeGen/RISCV/fixed-vectors-vsub-vp-mask.ll b/llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vsub-vp-mask.ll
similarity index 100%
rename from llvm/test/CodeGen/RISCV/fixed-vectors-vsub-vp-mask.ll
rename to llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vsub-vp-mask.ll